WO2006068504A1

WO2006068504A1 - Propeller arrangement

Info

Publication number: WO2006068504A1
Application number: PCT/NO2005/000484
Authority: WO
Inventors: Pål SOLLI; Lars Bjarne Berntsen
Original assignee: Goldfish Technology As
Priority date: 2004-12-23
Filing date: 2005-12-23
Publication date: 2006-06-29
Also published as: NO20045623D0

Abstract

The present invention regards a device to regulate the drag resistance of a propeller (3) arranged submerged in a liquid. One is adding gas to the liquid, with a device comprising a gas pipe (10) with control valve means (20) to regulate the amount of added gas to the liquid around the propeller (3). According to the invention there are means to read the pressure, for instance an open end of the gas pipe at the suction side of the propeller (3), which read pressure regulate the state of the control valve means (20) directly by the pressure difference across the control valve means (20).

Description

PROPELLER ARRANGEMENT

The present invention regards a device and method to regulate the drag resistance of a propeller in a liquid. It is especially suited for planing propelled boats

Propeller driven motor boats and especially turbo assisted diesel engines driven motor boats has a general challenge in that these engines quite often has a low torque and are relatively weak when running on low rotational speed. For a planing boat this is especially critical, since it is power demanding to overcome the planing threshold to get the boat into a planing situation where the resistance is reduced and thereby the speed increased.

There are several methods to overcome this critical planing threshold. One possibility is to do what has been done with land based vehicles, to introduce a gear box, for instance a mechanical gearbox or a disc coupling to make the engine work at the rotational speed where it is strongest. However this is not commonly used with planing boats since is has proven too costly and cumbersome to adapt land based gearbox system to a maritime environment and use.

Another method is to reduce the drag resistance of the propeller in the water by aerate the water around the propeller during the acceleration. By this the propeller blades will cavitate and "loose" their grip during the acceleration of the propeller and when wanted rotational speed and torque is high enough for maximum acceleration the aerating is choked.

In publication SE 457 164 there is described such a method where there in the exhaust gas channel is provided a diversion of some of the exhaust gas to the area of the propeller. The application focuses on arrangements to guide the exhaust gas into the propeller area. There is in the description mentioned that the amount of the exhaust gas to the propeller is regulated by a valve which is regulated by cable, by a electrical or fluid operated servo engine which are operated manually or automatically by electronic. Another possible method for aerating is described in US 4,545,711 where a part of the exhaust gas is guided to aerate the propeller until the propeller has a given rotational speed. This is achieved with velocity responsive valve means, where a valve body due to the rotation of propeller with the valve means will be forced against a spring and thereby closes the valve means. The outlet of exhaust gases in this publication is at the hub of the propeller. There is also in FR 2224344 described a system to aerate the propeller where gases are introduced on the suction side of the propeller in a distance from the propeller arrangement and regulated by a valve.

Neither of these solutions gives a system which is robust, easy to use and cost effective to be used in planing boats with a given range of size. It is an aim with the present invention to provide a robust, easy to use aerating system, which at the same time is cost efficient and which can be implemented on both existing and new boats.

It is also an aim to provide a device which is independent on the actual motor or propeller used in the boat for which the device should be used, making it possible to easily adapt it to any kind of boat and motor. It is also an aim to provide a system that is automatic and do not need manual interaction with the system to make it work.

These aims are achieved with a device and a method according to the invention as defined in the following claims.

There is provided a device to regulate the drag resistance of a propeller arranged submerged in a liquid, by adding gas to the liquid, comprising a gas pipe with control valve means to regulate the amount of added gas to the liquid around the propeller. According to the invention there are means to read the pressure at the suction side of the propeller. This read pressure, will then regulate the control valve means of the device. By this one achieves to regulate the amount of gas added to the liquid around the propeller without manual interactions of having to read other kinds of values of the system, as rotational speed of the propeller, motor resistance, flow measures etc. By this one achieves that for the necessary suction pressures around the propeller one achieves aeration and a reduced drag resistance of the propeller automatically. Since the device according to the invention is operated by the pressure on the suction side of the propeller and only this value there is no need to tune the device with the specific motor for which it should be used, when applying the system on an existing or new boat. There is as said no interaction between the device according to the invention and the motor running the propeller and it is therefore a possibility of adding the device according to the invention to already existing boats in an easy manner.

The gas pipe is a pipe leading form a source of gas down to the propeller. The source of gas may be air or exhaust gas or even a pressurized gas source. In a preferred embodiment the gas pipe comprises at least one open end at the suction side of the propeller faced towards the propeller, which open end reads the pressure at this position. This read pressure is transmitted through the interior of the gas pipe to the control valve means. This pressure is normally a negative pressure, since it is read at the suction side of the propeller. The open end is faced towards the propeller, and by this one should understand that an imaginary extension of a longitudinal axis of the gas pipe at the open end and out of the open end will either cross a main rotational plan of the propeller mainly transverse to a rotational axis of the propeller, or be parallel with this main rotational plane. The control valve means regulating the amount of gas lead to the liquid around the propeller, comprises a valve house and a valve body, where the position of the valve body is regulated directly by a pressure difference across the control valve means. The pressure difference across the control valve means is mainly equal to a pressure difference between the pressure of the source of the gas added through the gas pipe and the read pressure at the suction side of the propeller.

In the preferred embodiment the control valve means comprises at least an elastic element arranged between the valve house and the valve body, cooperating with the pressure difference across the control valve means to regulate the position of the valve body. The elastic element may be a spring with elasticity acting on the valve body against a pressure difference across the control valve means. There may instead of an elastic element be other arrangement acting on the valve body against a pressure difference across the valve means, for instance magnetism keeping the valve body out of abutment against a valve seat in the valve housing until the pressure difference across the valve means is lager than the magnetic forces, and thereby causing the valve body to abut the valve seat, against the magnetic forces.

In one possible embodiment the control valve means comprises two main positions or states of the valve means, one state is an open state when there is no or only a small pressure difference across the control valve means and the valve body is in a position not abutting any valve seats. In this state there may be some forces from an elastic element or caused by magnetism, on the valve element acting against the pressure forces crated by the pressure difference across the valve means keeping the valve element away from a valve seat in the valve house. The other state is a closed state when there is a larger pressure difference across the control valve means. In this state the pressure difference across the valve means creates a pressure force on the valve element larger than any forces acting on the valve element which then causes the valve element to abut against a valve seat in the housing, and thereby closes the valve means.

In another embodiment the control valve means comprises three main states, a first and second closed state when there is no or a small or a large pressure difference across the control valve means, respectively, and a middle open state when the pressure difference is in a medium range. This will give a closed state of the valve means with the valve body or valve element, abutting the valve seat, when there are no pressure difference across the valve means, and then when a pressure difference is created above a given value the valve means will move from the first closed state to the middle open state, and kept in this state until the pressure difference decreases again or increases until a new larger value where the valve means will move to the second closed state, when the valve body will abut a second valve seat.

In one possible embodiment this triple state valve may be accomplished by having at least two elastic elements with different stiffness, arranged between the valve house and valve body. The forces acting on the valve body from the elastic elements act against a force created by the pressure difference. These two elastic elements may be arranged in series or be arranged parallel, with both on one side of the valve body or one on each side valve body. The elastic element may preferably be a spring element, which acts either on compression or tension.

The elastic element or even magnetic systems will act as dampers on the movement of the valve element, being that with a compression spring with linear elasticity, the force from the spring will be proportional with the compression, i.e. the position of the valve element. This gives that if the spring is free in the first closed state for the valve element, it is partly compressed in the middle state and even more compressed in the second closed state, acting on the valve element with a much larger force in the second state than in the middle or first state. However, all the states for the valve means comprises a range of pressure differences across the valve means and has when looking at the actually valve element a gradually transition between the different states, i.e. the force acting against movement from the middle to the second state is largest just before the valve reaches the second state, most compression of the spring before the valve is actually closed, this also gives a dampening effect smoothing out the transitions between the different states of the valve. In an embodiment the control valve means comprises means to provide a part flow through the valve means in a closed position of the control valve means. It is also possible to envisage that the means to provide a part flow through the control valve means in a closed position comprises means to regulate the part flow down to zero flow. In another embodiment the means to read the pressure on the suction side of the propeller comprises sensor means and the device further comprises means to transmit the signals from the sensors to a control unit controlling the position of the control valve means regulating the amount of gas let out in the liquid around the propeller. One may have one or several openings of the gas pipe leading gas to the liquid around the propeller.

The invention will now be explained in further detail with reference to the accompanied drawings where:

Fig. 1 is a schematic side view of the device according to the invention positioned relative to a boat,

Fig. 2 is a schematic sketch of two states of one embodiment of a part of the device, Fig. 3 is a schematic sketch of three states of a second embodiment of a part of the device,

Fig. 4 shows another embodiment of a part of the device, Fig. 5 shows another embodiment of a part of the device, Fig. 6 shows yet another embodiment of a part of the device, and Fig. 7 shows yet another embodiment of a part of the device.

Similar elements in the figures are given the same reference numeral. These figures are non-limiting examples of embodiments of the present invention.

In fig. 1 there is shown a side view of a schematic sketch of the device according to the invention positioned relative to a boat 1 positioned relative to a body of water 2. To the boat 1 there is attached a propeller 3, driven by a not shown motor. The propeller 3 has a rotational axis 4, and several propeller blades 5, which when rotated forms a rotational plane for the propeller mainly transverse to the rotational axis 4. The propeller 3 has a normal suction side 6, which suction side normally is towards the normal traveling direction of the boat 1, towards the right in the fig.

The propeller 3 is submerged in the body of water 2. There may of course be several propeller arranged at the stern of the boat, with one device according to the invention for each propeller.

The device according to the invention comprises a gas pipe 10 for aerating the liquid around the propeller 3 at given pressures at the suction side 6 of the propeller 3. The device comprises within or at an end of the gas pipe 10, a valve means 20. This valve means 20 may be positioned below, or at least partly above the body of water 2. The gas pipe 10 comprises in this shown embodiment several bends 14A, 14B to adapt the device to fit the specific configuration of this type of boat. The gas pipe may have less or more bends 14 than shown in the figure. The gas pipe has an open end 12 at the suction side of the propeller 3, faced towards the propeller. An extension of a centre axis 11 of the gas pipe 10, from the open end 12 will cross the rotational plane for the propeller 3. The open end 12 of the gas pipe may be formed in many ways. There may be several openings of the gas pipe 10, the open end may be parallel with the rotational plane, and it may be positioned further down and to one or two or more sides. The position shown is favorable in respect to effect of the present invention and at the same time adding minimal drag resistance to the boat. It is also favorable to have the open en closer to an outer ends of the propeller blade 5 than the rotational axis 4 of the propeller 3. The gas pipe 10 has further a second open end 13, in this case where the gas added to the liquid is air, positioned above the body of water 2. This second open end 13, may in the case where the gas added is something other than air be positioned any other place in connection with the source of gas.

In fig. 2 there is shown a schematic sketch of two states of an embodiment of the valve means 20 of the invention. The valve means are shown in an open state A and a closed state B. The valve means comprises a valve house 21, which is connected to the gas pipe 10, the valve house 21 comprises a first valve seat 23, and within the valve house there is arranged a movable valve element 22. The valve house comprises further a bridge element 27, forming a connection point for an elastic element 25, attached between the valve house 21 and the valve element 22. The bridge element 27 is formed in such a manner that it influences the flow of gas through the valve means as little as possible. The spring element 25 tends to move the valve element 22 away from the valve seat 23 to an open state A of the valve means, as shown to the left. When the propeller starts to run there is created a negative pressure, a suction pressure, at the suction side of the propeller, this pressure is read by the open end of the gas pipe 10 and transmitted through this to the valve means, and then acting on the valve element 22. This will when the pressure difference across the valve means increases, i.e. in the case with air as gas, the difference between atmospheric pressure and the negative pressure at the suction side of the propeller, tend to move the valve element 22 against the force of the elastic element 25. When the pressure difference is equal to or larger than a preset value the valve element has been forced against the elastic element into abutment with the valve seat of the valve house and the valve means are closed. It will be closed until the pressure difference drops below the predetermined value, then the valve element will move away from the valve seat and open the valve means. In fig. 3 there is shown an embodiment with three different states of the valve means. A first closed state - A, a middle open state - B, and a third closed state C, where the different states of the valve means is dependent on the pressure difference across the valve means and the force from the elastic element 25. With no or a little pressure difference across the valve means the valve element 22 will be abutting the second valve seat 24 or the valve house 21, since there is an elastic element 25 arranged between the valve housing 21 and the valve element 22. When the pressure difference across the valve means increases, the resulting forces from this pressure difference will pull the valve element 22 against the spring force away from the valve seat 24 and into a middle open state giving free flow of gas through the valve means. When the pressure difference further increases the valve element 22 the forces will pull the valve element 22 into abutment against the first valve seat 23. In this embodiment the gas pipe 10 has in a T-shaped inlet to the valve means and a normal outlet. The spring element 25 tends to pull the valve element into a first closed state A. One may envisage that the spring element is used in an opposite way, giving that the spring element 25 will tend to press the valve element into a first closed state equal to state C, and then compressed in a middle and second state, instead of stretched.

In fig. 4 there is shown another embodiment of the valve means according to the invention. The arrangement is similar to the embodiment in fig. 3. In this embodiment the valve element 22 is more discs shaped and arranged in a cylinder shaped valve house 21, connected to the gas pipe 10. The valve element 22 in this embodiment comprises in addition means to form a part flow through the valve means in one closed state of the valve means in the form of grooves 35 in one side of the valve element, which grooves allow some gas through the valve means even when the valve element is abutting the first valve seat 23, forming a closed, but semi-closed state of the valve means.

In fig. 5 there is shown a somewhat different embodiment where the valve house comprises a bridge element 27, a rod 28 connected to the bridge element 27 and a stopper 29 arranged at the rod 28 in a distance away from the bridge element. The valve element 22 is arranged movable along the rod 28. There are two elastic elements 25, 26, with different elasticity, arranged between the stopper 29 and the valve element 22. Both elastic elements 25,26 are arranged on one side of the valve element 22, but it is possible to arrange them on opposite sides of the valve element 22. Having two different elastic elements with different elasticity gives a possibility to arrange them parallel or in series and give larger possibility of variety with respect to which intervals the valve means should go from one state to another. The valve element has in this embodiment also a specifically shaped part with a shape complementary to the valve seat 24. One may possibly also arrange sealing means 36 in the valve seat 24, or oppositely in the valve element (not shown). There is in this embodiment also arranged means to give a partly flow through the valve in a closed state, comprising of a bore 35 through the valve element 22, which may be equipped with system similar to the present invention internally within the bore, or other arrangement to regulate the flow through the bore 35.

In fig. 6 there is shown a different embodiment of the valve means according to the invention, in that there still is a valve house 21 and a valve element 22. However in this embodiment there are arranged magnetic elements 30,31 of different poles at, within or form parts of the valve house 21 and valve element 22, where similar poles will tend to keep elements away from each other and different poles will attract element towards each other. These magnetic forces will act against the forces created by the pressure difference across the valve means, similar to the spring elements in the previous embodiments.

In fig. 7 there is shown a further different embodiment of the invention. The means for reading the pressure at the suction side of the propeller is in this embodiment a sensor 40, transmitting signals through a signal line 41 to a control unit 42, which act in response to the signal and sends operation signals through signal line 41 to a operating cylinder 43, moving the valve means 20 in accordance with the read pressure by the sensor 40.

The invention has now been explained with several embodiments. A skilled person will however understand that there may be done several alterations and modifications to this embodiment within the scope of the invention as defined in the following claims.

Claims

1. Device to regulate the drag resistance of a propeller (3) arranged submerged in a liquid, by adding gas to the liquid, comprising a gas pipe (10) with control valve means (20) to regulate the amount of added gas to the liquid around the propeller (3), wh er ein there are means to read the pressure at the suction side of the propeller (3), which read pressure regulate the state of the control valve means (20).

2. Device according to claim 1, wherein the gas pipe (10) comprises at least one open end (12) at the suction side of the propeller (3) faced towards the propeller (3), which open end (12) reads the pressure, and the control valve means (20) comprises a valve house (21) and a valve body (22), where the position of the valve body (22) is regulated directly by a pressure difference across the control valve means (20).

3. Device according to claim 2, wher ein the control valve means (20) comprises at least an elastic element (25,26) arranged between the valve house (21) and the valve body (22), cooperating with the pressure difference across the control valve means (20) to regulate the position of the valve body (22).

4. Device according to one of the claims 2-3, wherein the control valve means (20) comprises two main states, an open state when there is no or a small pressure difference across the control valve means, and a closed state when there is a larger pressure difference across the control valve means.

5. Device according to one of the claims 2-3, wher ein the control valve means (20) comprises three main states, a first and second closed state when there is no or a small or a large pressure difference across the control valve means respectively and a middle open state when there pressure difference is in a medium range.

6. Device according to claim 5, w h e r e i n the control valve means (20) comprises at least two elastic elements (25,26) with different stiffness, arranged between the valve house (21) and valve body (22).

7. Device according to one of the preceding claims, wherein the control valve means (20) comprises means (35) to provide a part flow through the valve means (20) in a closed state of the control valve means (20).

8. Device according to claim 7, wherein the means (35) to provide a part flow through the control valve means (20) in a closed state comprises means to regulate the part flow.

9. Device according to claim 1 , w h e r e i n the means to read the pressure on the suction side of the propeller comprises sensor means (40) and the device further comprises means to transmit the signals from the sensors (40) to a control unit (42) controlling the position of the control valve means (20).

10. Method for regulating drag resistance of a propeller (3) arranges submerged in a liquid, by measuring the pressure at the suction side of the propeller (3) and regulating a control valve means (20) in a gas pipe (10) with an open end (12) at the suction side of the propeller (3) face towards the propeller (3), for regulating added gas to the liquid around the propeller (3).

11. Method according to claim 10, wherein the control valve means (20) are regulated by a differential pressure across the valve means (20), which differential pressure is created directly by the transmitting the pressure at the suction side of the propeller through the gas pipe (10) from the open end (12) and to the valve means (20), and the pressure of a source of gas for adding to the liquid around the propeller at the other side of the valve means (20).